Those of you that follow this blog know that I am not a big fan of using DMI fungicides on creeping bentgrass and annual bluegrass putting greens during the heat of summer. The impacts of these fungicides on bermudagrass greens, however, are not as well understood. Some of the newer DMIs, like Trinity, Triton and Tourney, are not labeled for application to ultradwarf bermudagrass varieties. Even though these products are safer on the cool-season grasses, they can cause severe phytotoxicity and thinning of 'Champion', 'Tifeagle' and 'Miniverde' greens.

A recent trial we performed on 'Champion' bermudagrass in Rocky Mount, NC showed some unexpected results. Each fungicide was applied once, on August 20, the day after the greens were hollow-tine aerified and topdressed. The plots were evaluated for phytotoxicity, turf quality, and recovery from aerification on September 1.

Not surprisingly, plots treated with Trinity, Tourney, and Triton FLO exhibited significant phytotoxicity and reduced turf quality as compared to the untreated control. Banner and Bayleton had similar effects, just not as severe as the others.

What was unexpected was the effect of the DMIs on recovery from aerification, as measured by the number of aerification holes still visible on Sept 1. Plots treated with Trinity, Tourney, and Triton FLO recovered almost as quickly as the untreated plots, whereas both Bayleton and Banner dramatically slowed recovery, especially Banner.

So, the take home message is, even though Bayleton and Banner are labeled for application to bermudagrass greens, these products can have adverse affects on the turf, in this case, slower recovery from aerification. More research is needed to fully characterize the effects of the DMIs on bermudagrass greens. In the meantime, I'd recommend avoiding applications of DMI fungicides either before or after hollow-tine aerification practices.

I do not have experience with the DMIs on Tifsport collars. I know that Tifsport tends to be pretty sensitive to growth regulators, so it would likely be a problem. Some of the new, safer DMIs on bentgrass could cause more injury to the collars.

How long after you spray will you normally start to see signs of phytotoxicity from DMI's? I am sure it depends on many factors but in general......I have a course that sprayed Sept 4 (tebuconozole) and it was not until nearly two weeks later we began to notice bronzing of the leaves. I was not there when that application was made nor the other fertilizer apps but my first thought was we would have seen the phytotoxicity much earlier so I thought it was some fert burn. But now leaning to it being from the DMI.

Injury from DMIs usually appears within a few days, but as you said it depends on many factors. I've seen cases where the purpling has shown up weeks later, and this is in research plots where nothing else had been applied. Tebuconazole could be the culprit in your case, but it's hard to say for sure.

Thank you. So the damage from DMI fungicides would be more of a purpling than a bronze to browning of the leaves?

Is there a list of pesticides that are not labeled or a list that are labeled for ultrdwarf bermudagrass greens? Or maybe even a list of pestcides to be careful with since I am sure it takes a lot of time and money to actually change labels for these new grasses.

Bronzing of the leaves is the most common symptom, but browning can occur as well. I am not aware of a list of products that are safe for the ultradwarfs. Just pay close attention to the labels, and before using a new product, always ask around to make sure that it is safe.

In the disease world, we've seen no problems with fungicides other than the DMIs on ultradwarf greens.

I have used Bayleton on Tifeagle with spray over onto TifSport collars and the effects were no different. This was a spring application for the prevention of Fairy Ring, and seemed to not have many adverse effects on either.

You say not to use before/after aerification, what kind of time frame would be safe. We wanted to do Fairy Ring prevention in early May, then core aerification in early June. Do you believe that would be adequate time?